Here's a recent example of a bill passing to allow this, but it's been allowed in various forms before this: https://www.washingtonpost.com/news/to-your-health/wp/2017/0...
Some patients are genuinely willing to contribute as research subjects in the hope of helping others, and this is a good reason to participate. What many people embarking on studies for new treatments do not realize, is that studies are not designed to benefit them personally (random assignation to placebo group, etc.). It is a common perception that people embarking on a clinical trial hoping for a miraculous cure have the wrong attitude, as there is little chance that you will be cured, and it will be a collateral effect even if it does happen.
PS: the above is a widely accepted opinion in current medical ethics.
All that to say, try to walk in a terminal patient's shoes for a bit, and perhaps you'll discover that the cost of increasing lifetime can be higher than you are willing to pay. Plus, we don't have the manufacturing and logistic capabilities to provide every possible experimental treatment to everyone.
Finally, you should realize that a lot of people have financial, academic, or even political interests to incentivize participation in clinical trials. It is precisely to avoid that, that patients must be informed that trials are not designed for one's personal benefit.
Even with stringent controls in place, there are plenty of examples where med/research companies skirt extremely close to the limits of ethical or exploitative behaviour.
"Might as well try it though"? Well, how about horrible side effects, a life that's longer but more painful and increasingly less dignified? Your last few months in a hospital far from family, vs your last weeks at home?
These are not straightforward issues.
Finally, consider that some terminally ill people simply don't want any more treatment. They're done with it all, and that's fine. This is a limiting factor in recruitment for trials for such situations.
I'm not denying your suggestion -- although these are conscious people with volition, which perhaps doesn't come across in your question. I'm just pointing out that ethics are very, very hard.
Cancer patients aren't unconscious and braindead. I agree with what you're saying but this is the argument used by medical boards.
https://www.cbsnews.com/news/polio-cancer-treatment-duke-uni...
http://www.dukechronicle.com/article/2016/05/poliovirus-canc...
You don't even have to be terminally ill to sign up, there are clinical trials for treatments for non-terminal conditions too.
2) Not all clinical trials have a control arm. It depends on the phase of the trial among other things.
TB is participating on clinical trials for effectiveness of Panitumumab in stage 4 colon cancer patients, its this drug that produced remission in his illness.
Original diagnosis was not wrong.